1. Field of the Invention
This invention relates to dispenser closures for tubular spouts through which pourable commodities may be dispensed by gravity or pressure induced flow from flexible plastic containers of, for example, bag-in-a-box packaging and more particularly is directed to the construction of such closures as spigot valves molded of elastomeric plastic resins.
2. Description of the Prior Art
My U.S. Pat. No. 3,400,866, U.S. Pat. No. 3,972,452 to W. C. Welsh and U.S. Pat. No. 4,211,348 to W. R. Scholle, being representative of the prior art, all utilize an integral valve formed as a closure diaphragm of elastomeric plastic material which opens by toggle action of a finger manipulatable tab projecting from a central region of the diaphragm, the toggle action serving to distort the normally closed concave configuration of the diaphragm.
A recognized problem in bag-in-a-box packaging is the permeability to gases of the elastomeric plastic materials from which the closure diaphragms must be made for proper functioning. Such permeability results in the undesirable exchange of gases through the diaphragm between the liquid contents of the package and the atmosphere, as for example, the entering of atmospheric oxygen permitting undesirable oxidation of the packaged product and also the loss of flavor essences from the product to the atmosphere. One solution to this problem suggests providing a gas impermeable barrier of sheet material to be applied externally to the tubular spout after the bag is filled and closed with the diaphragm. This solution has its own disadvantages including the requirement of additional packaging steps and modifications of existing automatic packaging machinery.
A need, therefore, exists for an improved dispenser closure which will provide the advantages of the resiliency of elastomeric material, preserve the compatibility with high speed automatic filling and sealing machinery in packaging and be capable of solving the problem of undesirable gaseous exchange.